Gasoline compositions

ABSTRACT

A gasoline composition is provided containing a major amount of a gasoline suitable for use in a spark-ignition engine, 1 to 15% v of ethyl levulinate, and 20 to 2000 ppmw of a nitrogen-containing detergent containing a hydrocarbyl group having a number average molecular weight in the range 750 to 6000.

FIELD OF THE INVENTION

This invention relates to gasoline compositions.

BACKGROUND OF THE INVENTION

WO 9421753 (VEBA OEL) discloses fuels for internal combustion engines, including both gasoline and diesel fuel, containing proportions (e.g. 1 to 90% v, 1 to 50% v, preferably 1 to 20% v) of esters of C₄ to C₆ keto-carbonic acids, preferably levulinic acid, with C₁ to C₂₂ alcohols. Esters with C₁ to C₈ alcohols are described as being particularly suitable for inclusion in gasolines, and esters with C₉ to C₂₂ alcohols are described as being particularly suitable for inclusion in diesel fuels.

The examples in WO 9421753 are all of the inclusion of quantities of levulinate esters in gasolines, for improvement in octane numbers (RON and MON). In Examples 1, 7 and 10, 10% v methyl levulinate is incorporated in different base gasolines. Examples 2 to 6 employ, respectively, ethyl levulinate, n-propyl levulinate, isopropyl levulinate, isobutyl levulinate and sec-butyl levulinate. Examples 8 and 9 employ 10% v of mixtures of methyl levulinate and methyl formate, in 1:1 and 2:1 ratios, respectively. Example 11 employs a range of proportions from 5% v to 90% v of methyl levulinate in unleaded Eurosuper gasoline.

WO 03002696 (AAE Tech. Int.) discloses a fuel composition incorporating levulinic acid, or a functional derivative thereof, with the object of providing more oxygen by volume than ethanol or traditional oxygenates such as MTBE or ETBE, giving little or no increase in fuel Reid vapour pressure and little or no effect on the flash point of the base fuel. The functional derivative is preferably an alkyl derivative, preferably a C₁ to C₁₀ alkyl derivative. Ethyl levulinate is said to be preferred, with methyl levulinate a preferred alternative. The levulinic acid or functional derivative is preferably used to form 0.1 to 5% v of the fuel.

One aspect of the disclosure of WO 03002696 further incorporates 0.1 to 5% v of a further additive selected from the groups consisting of:

-   a) the optionally alkoxylated linear or branched saturated or     unsaturated monoalcohols having 8 to 24 C atoms, containing zero or     1 to 20 mol of ethylene oxide and/or 1 to 5 mol of propylene oxide     per mol of alcohol, or -   b) the polyols having 2 to 6 carbon atoms, optionally partially     esterified with fatty acids having 1 to 24 carbon atoms, or -   c) the alkoxylated fatty acids having 12 to 24 carbon atoms and 4 to     20 mol of ethylene oxide per mol of fatty acid, or -   d) the ethoxylated dimeric fatty acids.     Such fuels are preferably diesel fuels (Page 7, lines 11 to 22).

In another aspect, the fuel is substantially free of alkoxylated compounds and of long chain alkyl alcohols, but it contains an additive of formula R—CO—NR¹R², where R is a saturated or unsaturated, linear or branched, alkyl radical having 6 to 21 carbon atoms (corresponding to number average molecular weight in the range 85 to 295), and R¹ and R² each independently represent a C₁ to C₄ hydroxyalkyl radical. An alternative additive (Page 8, lines 9, 10) comprises an oleic alkanolamide and an alkoxylated oleic acid.

Further provided is a fuel composition which incorporates the levulinic acid, or functional derivative thereof, together with a nitrogen source in the form of (Page 9 lines 8 to 15) a nitrogen compound selected from the group consisting of ammonia, hydrazine, alkyl hydrazine, dialkyl hydrazine, urea, ethanolamine, monoalkyl ethanolamine, and dialkyl ethanolamine wherein alkyl is independently selected from methyl, ethyl, n-propyl or isopropyl. Urea is preferred. The nitrogen compound may be an anhydrous compound or a hydrous compound, e.g. an aqueous solution, and may be up to a 5% w/w aqueous solution.

Cetane boosters, demulsifers and bio-diesel type fuels may also be present (Page 10, lines 1 to 29).

Whilst WO 03002696 states (Page 11, line 31) that “the foregoing is illustrated by the following examples”, the compositional and test result data consists of the following sentences:

“Specification gasoline blends containing up to 5.0% ethyl levulinate, 1.0% water and 2.0% non-ionic surfactant were found to have similar RVPs to the base gasoline.”, and

“Specification diesel blends containing up to 5.0% ethyl levulinate, 1.0% water and 2.0% non-ionic surfactant were found to have similar flash points to the base diesel.”

SUMMARY OF THE INVENTION

Accordingly there is provided a gasoline composition comprising a major amount of a gasoline suitable for use in a spark ignition engine, 1 to 15% v of ethyl levulinate, and 20 to 2000 ppmw of a nitrogen-containing detergent containing a hydrocarbyl group having a number average molecular weight in the range 750 to 6000. The preparation of such a composition, and its use in operation of a spark-ignition engine is also provided.

DETAILED DESCRIPTION OF THE INVENTION

It has now been found that gasoline compositions containing ethyl levulinate together with particular nitrogen-containing detergents can give enhanced engine cleanliness performance, and that gasoline compositions containing ethyl levulinate are more compatible with certain elastomeric seal materials than gasoline compositions containing similar concentrations of methyl levulinate.

Levulinate esters (esters of levulinic acid) and their preparation by reaction of the appropriate alcohol with furfuryl acetate are described in Zh. Prikl. Khim. (Leningrad) (1969) 42(4), 958-9, and in particular the methyl, ethyl, propyl, butyl, pentyl and hexyl esters.

Preferably, the ethyl levulinate concentration in the gasoline composition accords with one or more of the following parameters:

-   (i) it is at least 1.5% v, -   (ii) it is at least 2% v, -   (iii) it is at least 3% v, -   (iv) it is at least 4% v, -   (v) it is up to 12% v, -   (vi) it is up to 10% V, -   (vii) it is up to 8% v, -   (viii) it is up to 6% v,     with ranges having features (i) and (v), (ii) and (vi), (iii) and     (vii), and (v) and (viii) respectively being progressively more     preferred.

The gasoline composition preferably contains 50 to 1500 ppmw of the nitrogen-containing detergent, and more preferably 50 to 500 ppmw thereof. Quantities in the range 80 to 250 ppmw, e.g. 100 to 150 ppmw, are very suitable.

The nitrogen-containing detergent containing a hydrocarbyl group having a number average molecular weight (Mn) in the range 750 to 6000 may be an amine, e.g. a polyisobutylene mono-amine or polyamine, such as a polyisobutylene ethylene diamine, or N-polyisobutenyl-N′,N′-dimethyl-1,3-diaminopropane, or amide e.g. a polyisobutenyl succinimide, and are variously described, for example, in WO 0132812 and U.S. Pat. No. 5,855,629 which disclosure is hereby incorporated by reference. Alternatively, the nitrogen-containing detergent may be a Mannich amine detergent, for example a Mannich amine detergent as described in U.S. Pat. No. 5,725,612, which disclosure is hereby incorporated by reference.

A particularly preferred nitrogen-containing detergent is hydrocarbyl amine of formula R¹-NH₂, wherein R¹ represents a group R² or a group R²-CH₂— and R² represents a hydrocarbyl group having a number average molecular weight in the range 750 to 6000, preferably in the range 900 to 3000, more preferably 950 to 2000, and most preferably in the range 950 to 1350, e.g. a polybutenyl or polyisobutenyl group having a number average molecular weight in the range 950 to 1050.

The nitrogen-containing detergents are known materials and may be prepared by known methods or by methods analogous to known methods. For example, U.S. Pat. No. 4,832,702, which disclosure is hereby incorporated by reference, describes the preparation of polybutenyl and polyisobutenyl amines from an appropriate polybutene or polyisobutene by hydroformylation and subsequent amination of the resulting oxo product under hydrogenating conditions.

Suitable hydrocarbyl amines are obtainable from BASF A.G., under the trade mark “Kerocom”.

In addition to the ethyl levulinate and the nitrogen-containing detergent, the gasoline composition may additionally contain one or more carrier fluids, corrosion inhibitors, anti-oxidants, dyes, dehazers, metal deactivators, detergents other than a nitrogen-containing detergent containing a hydrocarbyl group as defined above (e.g. a polyether amine), friction modifiers, diluents and markers.

Particularly suitable carrier fluids are polyolefins, e.g. polyisobutylene and polyalphaolefins, and polyoxyalkylene compounds. Carrier fluids may conveniently be employed in total concentrations in the range 20 to 8000 ppmw, e.g. 50 to 500 ppmw.

Polyalphaolefin carrier fluids are primarily trimers, tetramers and pentamers, and synthesis of such materials is outlined in Campen et al. “Growing use of synlubes”, Hydrocarbon Processing, February 1982, Pages 75 to 82. The polyalphaolefin may be unhydrotreated, but it is preferably a hydrogenated oligomer. The polyalphaolefin is preferably derived from an alphaolefinic monomer containing from 8 to 12 carbon atoms. Furthermore, it preferably has viscosity at 100° C. in the range 6×10⁻⁶ to 1×10⁻⁵ m²/s (6 to 10 centistokes). Polyalphaolefins derived from decene-1 are very suitable. Polyalphaolefin having a viscosity at 100° C. of 8×10⁻⁶ m²/s (8 centistokes) are very suitable.

Polyoxyalkylene carrier fluids, which are very effective, preferably have the formula II

wherein R³ and R⁴ independently represent hydrogen atoms or hydrocarbyl, preferably C₁₋₄₀ hydrocarbyl, e.g. alkyl, cycloalkyl, phenyl or alkyl-phenyl groups, each R⁵ independently represents an alkylene, preferably C₂₋₈ alkylene, group, and p is such that Mn of the polyoxyalkylene compound is in the range 400 to 3000, preferably 700 to 2000, more preferably 1000 to 2000.

Preferably R³ represents a C₈₋₂₀ alkyl group and R⁴ represents a hydrogen atom. R³ preferably represents a C₈₋₁₈ alkyl group, more preferably a C₈₋₁₅ alkyl group. R³ may conveniently be a mixture of C₈₋₁₅ alkyl groups.

In the formula II the groups R⁵ are preferably 1,2 alkylene groups. Preferably each group R⁵ independently represents a C₂₋₄ alkylene group, e.g. an ethylene, 1,2-propylene or 1,2-butylene group. Very effective results have been obtained when each group R⁵ represents a 1,2-propylene group.

Number average molecular weights, e.g. of hydrocarbons such as polyalkenes, may be determined by several techniques which give closely similar results. Conveniently Mn may be determined by vapour phase osmometry (VPO) (ASTM D 3592) or by modern gel permeation chromatography (GPC), e.g. as described for example in W. W. Yau, J. J. Kirkland and D. D. Bly, “Modern Size Exclusion Liquid Chromatography”, John Wiley and Sons, New York, 1979. Where the formula of a compound is known, the number average molecular weight can be calculated as its formula weight.

Very suitable friction modifiers are the fatty acid salt friction modifiers disclosed in DE-A-19955651 (BASF) (e.g. that described in Example 1 thereof), e.g. in an amount in the range 5 to 1000 ppmw, preferably 25 to 400 ppmw, and more preferably 50 to 200 ppmw.

Typical of gasolines suitable for use in spark ignition engines are mixtures of hydrocarbons having boiling points in the range from 25° C. to 232° C. and comprising mixtures of saturated hydrocarbons, olefinic hydrocarbons and aromatic hydrocarbons. Preferred are gasoline blends having a saturated hydrocarbon content ranging from 40 to 80 per cent volume, an olefinic hydrocarbon content ranging from 0 to 30 per cent volume and an aromatic hydrocarbon content ranging from 10 to 60 per cent volume. The gasoline can be derived from straight run gasoline, polymer gasoline, natural gasoline, dimer- or trimerised olefins, synthetically produced aromatic hydrocarbon mixtures from thermally or catalytically reformed hydrocarbons, or from catalytically cracked or thermally cracked petroleum stocks, or mixtures thereof. The hydrocarbon composition and octane level of the gasoline are not critical. The octane level, (R+M)/2, will generally be above 85. Any conventional gasoline can be used. For example, in the gasoline, hydrocarbons can be replaced by up to substantial amounts of conventional alcohols or ethers conventionally known for use in gasoline.

The gasoline is preferably lead-free, and this may be required by law. Where permitted, lead-free anti-knock compounds and/or valve-seat recession protectant compounds (e.g. known potassium salts, sodium salts or phosphorous compounds) may be present.

Modern gasolines are inherently low-sulphur fuels, e.g. containing less than 200 ppmw sulphur.

In this specification, amounts (concentrations) (% v) (ppmw) of components are of active matter, i.e. exclusive of volatile solvents/diluent materials.

The invention further provides a process for the preparation of a gasoline composition of the invention as defined above which comprises bringing into admixture the gasoline, the ethyl levulinate and the nitrogen-containing detergent.

If desired, the fatty acid salt, the co-additive, and any additional components such as corrosion inhibitors, anti-oxidants, etc., as listed above, may be co-mixed, preferably together with suitable diluent(s), in an additive concentrate, and the additive concentrate may be dispersed into gasoline, in suitable quantity to result in a composition of the invention.

The invention also provides a method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of the invention as defined above.

The method of the invention may lead to any of a number of advantageous effects, including good engine keep-clean performance, especially in relation to inlet-system deposits, and clean-up performance can be achieved at the higher concentrations of the nitrogen-containing detergent, advantageous octane performance (RON and MON) and advantageous Reid vapour pressure.

The invention will be further understood from the following illustrative examples in which, unless otherwise indicated, parts and percentages are by weight and temperatures are in degrees Celsius.

In the examples, base fuel used was an unleaded gasoline (95 ULG) of RON 98.9, MON 86.6, and having sulphur content (ASTM D 2622-94) of 138 ppmw, aromatics content of 50.7% v/v and olefins content 7.5% v/v (ASTM D6623-01 (procedure C)), Density (DIN 51757/V4) 779.1 kg/m³, distillation (ISO 3405/88) IBP 35.42, 95% v/v 174.4, FBP 203° C.

Fuels were blended with additives by adding additive to base fuel at ambient temperature (20° C.) and homogenising.

The following additives were used:

Ethyl levulinate (ex Avocado Chemicals, cat. No. 15001);

-   “DP” —this was a standard commercial gasoline additive package,     containing a polyisobutyleneamine detergent, a synthetic carrier oil     and a conventional corrosion inhibitor, corresponding closely to     additive package PI of Example 3 of DE-A-19955651. The     polyisobutyleneamine detergent was a polyisobutylene monoamine     (PIBA) ex BASF, in which the polyisobutylene (PIB) chain has a     number average molecular weight of approximately 1000. The synthetic     carrier oil was a polyether carrier being a polyoxypropylene glycol     hemiether, containing 15 to 30 propylene oxide units prepared using     a mixture of alkanols in the C₅₋₁₅ range as initiators, and having     Mn in the range 1000 to 2000. The additive package contained about     68% in non-volatile matter, about 27% w of the package being the     PIBA and 40% w of the package being carrier fluid. -   “PIBA” —this was technical polyisobutylene monoamine corresponding     to that in “DP”, containing 50 to 55% w active matter, the balance     being essentially unreacted polyisobutylene.

Test fuels were subjected to engine testing according to the following procedure.

Toyota Keep Clean

In order to evaluate inlet valve cleanliness, an IVD Keep-clean test was carried out using a Toyota 2.0 litre 3S-FE engine taken from a 1992 model Toyota Carina having 4 valves per cylinder. The engine is multi point injected (MPI), has a lambda sensor and exhaust gas recirculation.

Before commencing the test, inlet parts and combustion chambers were cleaned and new pre-weighed inlet valves and new spark plugs fitted to the engine, a new oil filter was fitted and the engine filled with new engine oil.

The engine was run for a period of 69 hours under a test procedure corresponding to that of CEC-F-05-A-93, except that the Toyota 3S-FE engine was used in place of the Mercedes Benz M 102 E engine specified in the CEC-F-05-A-93 procedure, and the torque values differ from those specified in CEC-F-05-A-93 to compensate for the different BMEP (break mean effective pressure) values achieved by the Mercedes Benz M 102 E and the Toyota 3S-FE engines.

The specific conditions of each cycle were: Stage time (secs) rpm torque (Nm) 1 30 850 idle 2 60 1300 26 3 120 1850 28 4 60 3000 30

Upon completion of the test, the engine was stripped and the valves re-weighed to give the inlet valve deposit (IVD) weight.

EXAMPLE 1

In this example, gasoline compositions were prepared containing 5% by volume of ethyl levulinate and 380 ppmw of DP (Example 1), 380 ppmw of DP (Comparative Example A), 5% by volume of ethyl levulinate (Comparative Example B), and these were tested by the above procedure in comparison with base fuel (Comparative Example C). Results are given in Table 1. TABLE 1 Ethyl levulinate DP IVD Example (% v) (ppmw) (mg/valve) 1 5 380* 4 Comparative A 0 380* 26 Comparative B 5  0 111 Comparative C 0  0 142 *corresponds to about 105 ppmw of PIBA active matter

The above results clearly show a very surprisingly superior keep-clean performance for the fuel containing both ethyl levulinate and polyisobutylene amine relative to fuels containing one or other of ethyl levulinate and polyisobutylene amine, or neither of these materials.

EXAMPLE 2

In order to ascertain and demonstrate that significant enhancement of keep-clean performance was due to simultaneous presence of the ethyl levulinate and polyisobutenyl amine, gasoline compositions, using a base fuel prepared to the same recipe as that of Example 1, were prepared containing 5% by volume of ethyl levulinate and 225 ppmw PIBA (Example 2) and 225 ppmw PIBA, (Comparative Example D) and these were tested by the above procedure. Results are given in Table 2. TABLE 2 Ethyl levulinate DP IVD Example (% v) (ppmw) (mg/valve) 2 5 225* 13 Comparative D 0 225* 24 *corresponds to 110 to 125 ppmw of PIBA active matter

The results shown in Table 2 do indeed confirm that significant and surprising enhancement of keep-clean performance was due to the presence of both ethyl levulinate and polyisobutenyl amine in the fuel blend of Example 2.

EXAMPLE 3

Tests were carried out to investigate compatibility of fuels containing ethyl levulinate with seal materials, in comparison with base fuel and with fuels containing methyl levulinate (ex Aldrich, cat. No. 61405).

The test procedure was a modified version of ISO 1817:1998. Two elastomeric materials were tested, viz. a hydrogenated nitrile elastomer (“Elast-o-Lion” 280 (trade mark), ex James Walker & Co. Ltd., UK) and a fluorocarbon tetrapolymer elastomer (“Viton” (trade mark) LR 6316, ex James Walker & Co. Ltd., UK). Volume and Shore hardness values of elastomer samples of dimensions 50 mm×25 mm×3 mm were measured before testing, and again after immersion in 100 ml of test fluid at ambient temperature (20° C.) for 168 hours. Samples were weighed in air and in water (for assessment of volume). After immersion in test fluid for 168 hours, the samples were quickly dried, weighed in air and in water (within 8 hours of removal from the test fluid), and percentage changes in volume were calculated. Hardness was measured at ambient temperature using a “Type A Shore Durometer” (trade mark) (ex. Shore Instruments, Instron Corp., USA).

Results are given in Table 3. TABLE 3 Elastomer Hydrogenated Fluorocarbon Levulinate nitrile tetrapolymer Concentration % Volume % Hardness % Volume % Hardness Test Sample Levulinate (% v) change change change change Comparative P — 0 22.0 −12.8 2.7 −2.8 X Ethyl 2 28.1 −14.2 6.0 −4.9 Y Ethyl 5 34.4 −16.2 12.4 −9.3 Z Ethyl 10 43.9 −18.6 25.6 −14.6 Comparative Q Methyl 2 31.7 −18.6 6.5 −3.7 Comparative R Methyl 5 41.6 −18.9 17.0 −10.2 Comparative S Methyl 10 59.2 −20.9 36.7 −15.9

As can seen from the above results, for any given concentration, the effects of ethyl levulinate are significantly less deleterious than those of methyl levulinate, since higher percentage changes are associated with increased risk of leakage from seals. 

1. A gasoline composition comprising a major amount of a gasoline suitable for use in a spark ignition engine, 1 to 15% v of ethyl levulinate, and 20 to 2000 ppmw of a nitrogen-containing detergent containing a hydrocarbyl group having a number average molecular weight in the range 750 to
 6000. 2. The gasoline composition of claim 1 wherein ethyl levulinate is present in an amount of 1.5 to 12% v.
 3. The gasoline composition of claim 1 wherein ethyl levulinate is present in an amount of 2 to 10% v.
 4. The gasoline composition of claim 1 wherein ethyl levulinate is present in an amount of 3 to 8% v.
 5. The gasoline composition of claim 1 wherein ethyl levulinate is present in an amount of 4 to 6% v.
 6. The gasoline composition of claim 1 wherein the nitrogen-containing detergent is present in an amount of 50 to 1500 ppmw.
 7. The gasoline composition of claim 5 wherein the nitrogen-containing detergent is present in an amount of 50 to 500 ppmw.
 8. The gasoline composition of claim 1 wherein the nitrogen-containing detergent is a hydrocarbyl amine of formula R¹-NH₂, wherein R¹ represents a group R² or a group R²-CH₂— and R² is a hydrocarbyl group having a number average molecular weight in the range 950 to
 1350. 9. The gasoline composition of claim 8 wherein ethyl levulinate is present in an amount of 3 to 8% v.
 10. The gasoline composition of claim 9 wherein the nitrogen-containing detergent is present in an amount of 50 to 1500 ppmw.
 11. A process for the preparation of a gasoline composition comprising bringing into admixture a gasoline suitable for use in a spark-ignition engine, 1 to 15% v of ethyl levulinate and 20 to 2000 ppmw nitrogen-containing detergent containing a hydrocarbyl group having a number average molecular weight in the range of 750 to
 6000. 12. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 1. 13. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 2. 14. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 3. 15. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 4. 16. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 5. 17. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 6. 18. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 7. 19. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 8. 20. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 9. 21. A method of operating a spark-ignition engine, which comprises bringing into the combustion chambers of said engine a gasoline composition of claim
 10. 